According to HRW's report, the spate of extrajudicial killings began after the 2010 elections, won by President Pierre Nkurunziza and his CNDD FDD party. Burundian human rights groups estimate there have been as many as 300 such killings.

Nkurunziza’s party faced no challengers at the ballot box after the main opposition parties formed a coalition and boycotted the vote, charging intimidation and electoral fraud. Coalition members, including the rebel-group-turned-political-party Forces Nationales de Liberation (FNL), fled to the bush or nearby Congo, leaving the country’s political opposition largely fragmented.

The report identifies a subsequent pattern of retaliatory attacks, where former opposition supporters often fall victim to state security forces, intelligence services, and the CNDD-FDD’s youth group.

Although the majority of political killings documented by HRW targeted the opposition, members of the ruling party have also been assassinated in "tit-for-tat” attacks. Interviews with family members of victims killed because of their association with CNDD-FDD suggest FNL are behind the murders.

But according to one Bujumbura-based human rights activist, even the politically unaffiliated are at risk.

“In Bujumbura-rural, where there is FNL, what they do is kill those who are not with them," says Lionel, who declined to provide a last name. "They say, 'You are with us, you come with us, or you don’t come with us, and we kill you.'”

Massacre in Gatumba, Bujumbura Rural Province

The report also provides a detailed account of a massacre in the town of Gatumba, where 37 died last September. The government blames a furtive, anonymous opposition, while others claim the government orchestrated the massacre to frame its enemies. The government established a commission of inquiry given 30 days to investigate the attacks. The commission’s report, completed in October, has yet to be released.

HRW’s own investigations into the massacre found that only one witness from Gatumba had been contacted by the government’s inquiry commission.

Last November, 21 people accused of being involved in the attack were brought to trial, which, despite the large number of defendants, concluded so quickly it drew critical statements from both the Bujumbura Bar Association and the European Union, which both cited procedural irregularities and a neglect to call key witnesses.

Following the Gatumba massacre, the Burundian minister of communication ordered a 30-day media blackout.

Pierre Claver Mbonimba, a prominent human rights activist who has been documenting the political killings, counted 123 executions between May and July of 2011.

“I receive calls from the Ministry of the Interior - they threaten to shut our organization down," he says. "They send letters of warning every time I denounce the political violence. I’ve already received four. Two in 2011 and two in 2012.”

In January, Mbonimba’s home was broken into. He suspects the government sent the 12 armed men.

Burundi is still healing from the wounds of a 12-year civil war that formally ended in 2005. Despite the absence of an organized political opposition, the CNDD-FDD party faces growing dissent, and rumors suggest a rehabilitated FNL and two rebellions based in Tanzania and Congo have been declared.

In March, the International Crisis Group published a report describing a deepening crisis of corruption in the country.